Structural connector



A. 13, 39*"; CRQT STRUCTURAL coNNEdToR Filed Feb. 7, 1944 \K\ ///I V/ [A 7 IN VEN TOR. ANDRE EH47? AGENT F'atented Aug. 13, 1 946 2,405,643 STRUCTURAL CONNECTOR Andr Crot, Los Angeles, Calif., assignor to Lockheed Aircraft Corporation, Burbank, Calif.

Application February 7, 1944, Serial No. 521,477

6 Claims. (Cl.'189--36) This invention relatesto structural connections, and relates more particularly to connectors for aircraft structures and other assemblies.

It has long been the general practice to employ rivets, screws and welding to connect airplane parts and components. At points where it is necessary to service or inspect instrumentalities within the aircraft assembly it is the practice to provide access openings and to equip such openings with closures secured in place by releasable fasteners. The installation of multiplicities of rivets or screws, or the making of numerous welds is laborious, expensive and time consuming. Furthermore, there are many situations where the joints are inaccessible, at least at one side of the assembly, necessitating the employment of blind rivets, plate nuts, and the like. Where removable panels; closures, etc, are used, numerous releasable fastening devices are required and considerable expense is involved in the installation.

It is a general object of the present invention to provide simple, dependable structural connectors for use in aircraft asemblies, and other structures where preformed or prefabricated components are to be assembled, that obviates the necessity for employing rivets, screws and welds in the final assembling of the parts, sections or components. The joints or connecting devices of the invention eliminate the need for rivets, screws, and the like, in finally connecting the sections or components of the assembly and make it unnecessary to employ blind rivets, plate nuts or similar expedients in situations where the joints are inaccessible or inaccessible in part.

Another object of the invention is to'provide structural connectors of the character referred to that are strong and dependable and positively connect the parts, sections or components of the assembly. The connectors are designed to effectively resist longitudinal shear as well as forces acting in all other directions and have a strength equal to or greater than the parts or components which they connect.

Another'object of the invention is to provide structural'connectors of the character mentioned that may be easily and quickly assembled without special tools or equipment.

A further object of theinvention is to provide connectors of the general class referred to which present smooth flush or substantially flush surfaces at the joints and avoid all irregularities at the joints.

A still further object of the invention is to provide structural connectors of the class referred to that may be quickly released to permit disconnection of the assembled parts or sections. The connectors are strong and. positive when assembled or made up and are not subject to failure or disconnection by vibration, but may be intentionally released with ease'when it is desired to remove or disconnect the associated parts or sections. This feature of the invention particularly adapts the connectors for use with closures, panels or sections that are intended to be removed for the purpose of inspecting or servicing elements Within the assembly.

Other objects and features of the invention will be readily understood from the following detailed description of typical preferred forms of the invention wherein reference Will be made to the accompanying drawing in which,

Figure 1 is a fragmentary perspective view of a typical aircraft assembly of the type in which connectors of the invention may be utilized;

Figure 2 is an enlarged transverse detailed sectional view of one form of joint or connection of the invention showing it associated with parts of an assembly;

Figure 3 is a fragmentary longitudinal detailed sectional view taken substantially as indicated by line 3-3 on Figure 2;

Figure 4 is a view similar to Figure 2 illustrating anotherform of connector of the invention;

Figure 5 is a fragmentary longitudinal detailed sectional view taken as indicated by line 5-5 on Figure 4 but showing the lock strip before it is locked; and,

Figure 6 is a view similar to Figure 2 illustrating still another embodiment of the invention.

The joints or connectors of the invention are suitable for use in many different situations and in structures varying greatly in character. Furthermore, the invention is capable of substantial modification to adapt the connectors for given purposes and for use in given assemblies. I will herein describe the invention as employed in aircraft structures, it being understood that this is merely a typical application and is not to be construed as limiting either the scope or the utility of the invention.

In Figure 1 of the drawing I have illustrated a portion of an aircraft boom 0r fuselage comprising two sections S adapted to be connected by a joint structure or connector of the invention. Furthermore, the individual sections 5 are substantially cylindrical tubular elements and their axial seams or joints Ill may be provided with selected connectors of the invention. It is to be understood that the airplane assembly of Figure 1 is merely typical of many structures in which 3 theconnectors of the invention may be employed and the invention is not to be considered as limited for use on tubular assemblies or assemblies of any particular configuration.

Figures 2 and 3 of the drawing illustrate a typical preferred form of connector of the invention which comprises two members II formed to have locking cooperation one with the other, and a lock strip'IZ for holding the members H in the interlocking relation.

The members I I are intended to be secured to the edge portions of the components or sections A which are to be connected. In the drawing, the adjacent edge portions of the sections A are flat, it being understood that the connector may be used with sections that are curved or contoured. The members I I are alike or complementary and where. the connector is to be II may be formed of a suitable aluminum alloy.

Inpractice the members II may-be extruded sections of aluminum alloy or the like. The members I I resemble angle sections and have broad or extensive flanges I3 and inturned flanges I4 of less extent. The flanges l3 are intended to be attached to their respective components or sections A of the assembly. The flanges I3 may flatly or evenly engage the inner surfaces of the sections A and may be contoured to .conform to contoured sections, although in most cases the flanges I3 are sufficiently flexible to readily conform to such contoured sections. In accordance with the invention, the flanges I3 are permanently secured to the sections A tobe rigid therewith. The flanges I3 may be attached to the sections A by rivets 9, screws, spot welds, or roll welds. It is usually preferred to positively secure the flanges I3 to their respective sections A throughout the lengths of the flanges.

The inturned flanges .I4 of the members II are in the nature of rims .or beads which preferably extend throughout the entire lengths of the members. The flanges I4 extend along the inner or opposing edges of the flanges I3 and are thickened to have bulbs I5 which present convex surfaces or shoulders I6 at what I will term the rear faces of the flanges I4. The inner and outer corners of the-flanges 14 are also preferably rounded about suitable radii. In the preferred construction the forward sides or faces of the flanges M are formed to have looking or meshing cooperation to assume the longitudinal shear forces to which the assembly may be subjected. Multiplicities of teeth or serrations I! are provided on the forward faces of the flanges I4. The serrations I! may be of any selected cross sectional configuration. It is usually preferred to employ serrations I! of V-shaped cross section, as illustrated in Figure 3, to provide maximum contact and to assure. full uniform mating of the serrations. The series of serrations I! may extend throughout the entire length of the connector and may be of substantial Width. In forming the serrations the flanges I3 of the two members may be arranged. in back-to-back relation, and the two members then may be simultaneously passed through a roll machine to form identical serrations I! in the faces of the tow flanges I4. This mode of forming the serrations I'I assures perfect mating or cooperation of the serrations when the connector is assembled. The members ,II are attached to the sections A to be in the relationship where their serrations mesh when the sections A are brought 4 into the required assembled positions. It will be seen that when the serrations II are in full mesh the connector is capable of assuming extremely heavy longitudinal shear loads.

The lock strip I2 is provided to retain the members II in the positions where their serrations H are in full mesh and further serves to lock or hold the members II against relative transverse movement or displacement. The lock strip I2 is channel shaped or substantially U-shaped in transverse cross section having two spaced side parts I 8. The strip I2 is shaped and proportioned to engage around the interlocking flanges I4 and its side parts I8 are shaped to cooperate with the flanges. Enlargements or bulbs I9 are provided on the inner surfaces of the side parts I8 and present convex rounded shoulders 20 for cooperating with the shoulders I6 of the flanges I4. The flanges I4 have curved concave external surfaces adapted to receive the bulbs I9 to allow full engagement of the shoulders 20 with the shoulders I8. When the sections A have been brought to the relationship where the serrations I! are in meshing engagement, the lock strip I2 is slid onto the flanges I4 to bring the shoulders 20 into engagement with the shoulders I6. This looks the connector so that the sections A are positively connected against relative movement and displacement in all directions. The Walls of the trough or channel 2I in the lock strip I2 are shaped to conform to or readily receive the bulbed edges of the flanges I4. The lock strip I2 may be proportioned to extend throughout the entire length of the joint and is preferably uniform in transverse configuration to have even engagement with the flanges I4.

Means may be provided to prevent longitudinal displacement or movement of the lock strip I2. This means may comprise a pin or screw 22 engaged in openings in the strip I2 and a The pin or screw 22 is preferably adjacent one end of the connector to be accessible. There is little or no tendency for the lock strip I2 to move longitudinally and the screw 22 is not required in all installations. In some instances a holding means for the lock strip I2 is entirely unnecessary. For example, in some structures elements of the assembly may engage the opposite ends of the lock strip I2 to hold it against endwlse movement.

In situations where the joint or connector is subject to heavy transverse shear loads it may be desired to employ a, key 23 to assist in assuming such loads. Where the key 23 is to be used, partially cylindrical longitudinal grooves 24 are provided in the serrated forward faces of the flanges I4. Th grooves 24 oppose one another and register to constitute a cylindrical opening for receiving the cylindrical key 23. 'The key 23 is passed or slid into this opening from one end of the assembly. It will be seen that the key 23 engaged in the grooves 24 is capable of assuming heavy transverse shear loads that may be imposed on the assembly. The key 23 is optional and is not required in all cases. Where the :key 23 is not used the channel shaped lock strip I2 conforming to the flanges I2 and the bulbs I5 thereon positively prevents relative transverse displacement of the assembled sections A and dependably assumes transverse shear loads. Furthermore, the lock strip I4 engaging about the flanges I4 prevents separation of the sections and dependably transmits and assumes tension to which the assembly may be subjected.

From the above it will be seen that the connector illustrated in Figures 2 and 3 is easily made nal shear loads and the key 23 and lock strip.

l2 engaged with the flange parts [4 dependabjly hold the connected sections. against relative movement in all other directions. The connectionis strong and positive and will not work loose under any conditions of operation orv usage. When it is desired to disconnect the sections A, the lock strip 12 is merely slid from the flanges l4, and where the key 23 is employed the key is withdrawn from the grooves 23. This frees the sections A for disconnection.v Th connector i1- lustrated in detail in Figures 2 and 3 is used at the axial joints I!) in the assembly of Figure 1; this being one typical application of the connector.

Th joint or connector illustrated in Figures 4 and 5 is such that it may be assembled or made up from the exterior of the structure and is therefore advantageous in situations where the interior of the structure is inaccessible. The connector is useful with closures for access openings, and the like, although not limited to such applications, and in Figure 1 I have shown the connector joining the two sections S of the boom assembly. The construction of Figures 4 and 5 comprises two members 30 connected to the assembly sections B and formed to have meshing or interlocking cooperation, and a locking strip 3! for holding the members 30 in the interlocking relationship.

The members 39 are secured to the edge portions of the sections B as by rivets 32, screws orwelding. The members 30 are identical angular elements and when formed of an aluminum or magnesium alloy, may be extruded sections. It is preferred to provide the members 36 with flanges 33 similar to the flanges l3. The flanges 33 are arranged against the inner faces of the sections B and are secured to the sections by the rivets 32 or other selected attaching means.

The members 3Q further include inturned or inwardly projecting flanges 34 on the main flanges 33. The flange t-t are substantially U or J -shaped in transverse cross section extending inwardly from the flanges 33, then curving later-p ally in substantially parallel relation to the planes of the sections B and then extending outwardly ortoward said plane. I will term the outwardly extendingportions, flange parts 35. .Bulbs 36 are provided on the outer edge portions of the flange parts 35. The bulbs 36 present curved or convex shoulders in the troughs of the J flanges 34. h In accordance with the invention, the opposing faces of the flange parts 35 have multiplicities of teeth or serrations 31. The series of serrations 341 preferably extend throughout the lengths of the flange parts 35 and the serrations of the two members are identical to accurately mesh. Ihave shown the serrations 31 of V- shaped transverse cross section, and the serrations 31 may be formed in the same manner as the serrations H.

The locking strip 3| is an elongate element. de-

The mating serrations g 6 signed to engage iaboutthe flange part 35 to" hold them in the relationship where their serration 31.1are in complete mesh. 'Wherethe connector parts'are formed of aluminum alloy, or the like, the strip 3| maybe an extruded section. The strip 3| is channel shaped in transverse cross section having two spaced generally parallel side parts 31* and a connecting portion 38. The side part 3% ar proportioned to fit within the troughs of the J-shaped flanges 2M. Bulbs 39 are provided on the side partsti and engage under or interlock with the bulbs 36 of the flange parts 35-. Figure 4 clearly illustrates the manner in which the bulbs 36 and 39engage or interlock, to retain the members 30 and their sectionsB in the correctly assembled relationship. It will be observed that the'bulbed flange parts 35(substantially conform to the trough of the lock strip 3! with the bulbs 3E engaging over the bulbs 39'. This interlocking engagement of the strip 3| and member 30 positively holds the sections B against relative transverse displacement and maintains the serrations 3'. in mesh for the dependable transmission of longitudinal shear loads. It is preferred to make the outer face E6 of the lock strip 3! flat or of thesame contour as the sections B and to proportion the parts so that the face 49 lies flush with the outer surfaces of the sections B. This provides a flush joint and is of importance in aircraft where aerodynamic designs require flush joints. The lock strip 3| may be readily slidto the position where'it cooperates with the flange parts 35 throughout the entire-length of the connection; The strip 3! is merely entered intothe connection at one of its ends and advanced to .its flnal position. If required, the. strip 3! may be secured in its final position by a screw or pin 4! engaged in openings in the strip and a part 35 adjacent one end of the connector.

The connector of Figures land 5 may be constructed to provide for the quick ready assembly. of the sections B. The parts may be formed so that the lock strip 3! may be assembled in its final. position by merely introducing the side parts 3? into the troughs of the flanges 34; and then shifting the strip a short distance in either longitudi" nal direction. As best illustrated in Figure 5, the bulbs 36 of the flange parts 35 have pluralities of spaced interruptions or notches 42. The notches 42 may be equally spaced and formed to leave teeth or projections 53 of equal width. The bulbs 39 of the parts 3i have similar spaced interruptions or notches 44 leaving teeth or projec tions 45.

In assembling the construction of Figures 4 and 5, the sections B are first brought to the positions where the serrations 31 are in full meshing engagement. The strip 3i is then arranged so that its side parts 3'! enter the troughs of the flanges 3E and. the strip is lowered or pressed inwardly so that the projections 45 I pass through the notches 42. Figure 5 illustrates this position of the strip 3|. The strip 3| is then moved l ngi tudinally in either direction a distance equal to the width of theprojections 53 so that the pro- J'ections 45 of the bulbs 39 engage under the projections 4 30f the bulbs 35, The strip 3i may then be secured in this position by-the pin or screw 4|. It will be observed that the connection may be readily assembled in situations where it is difiicult tice may be cut from the'same length of stock.

The members 41 are elongate elements having main flanges 49 which may be secured to the sections C of the assembly by'screws or rivets 58. Where the parts are formed of an aluminum or magnesium alloy, the members 41 may be extruded parts. The member 41 may extend throughout the entire length of the joint or connection.

The members 41 ar further provided with what I will term flange-parts The flange parts 55 extend along the adjacent or opposite edges of the members 41 and theirforward or opposing faces areserrated. The faces of the flange parts 5| are provided with serrations 52 similar to the above described serrations l1 and 31. The errations 52 are adapted to mesh when the sections C are in the correct assembled relationship. The mating serrations 52 of the two members 41 are capable of assuming very heavy longitudinal shear loads.

The flange parts 5! are haped to receive the internal lock key or strip 48. Each part 5| has a longitudinally extending opening 53 and a slot 54 extending from its serrated fa'ce'to join the opening 53. The slots 54 have flat generally parallel walls lying in planes parallel with the plane occupied by the sections 0. The walls 55 of the openings 53 at the ends of the slots 54 are flat and substantially normal to the walls of the slots.

The locking strip 48 is inserted in the slots 54 and openings 53 to positively lock or key the members 41 together in the assembled relation where the serrations 52 are, in mesh. The key strip 48 is shaped, to generally conform to the slots 54 and openings53. The strip 48 may be an extruded section of aluminum alloy, or the like, where the members 41 are formed of such material. The lock strip 48 has a central web 56 and thickened portions or beads 51 which extend along its longitudinal edges. The web 56 is shaped and proportioned to fit the slot 54'and the beads 51 are shaped to freely flt the openings 53. The web 56 may have flat surfaces for engaging with the flat walls of the slots 54 and the beads 51 prererably have shoulders 58 for engaging with the walls 55 of the openings 53.

In assembling the connector of Figure 6, the sections C are first brought to the correct assembled relationship Where the, serration 52 are in full mesh. The key strip 48 is then inserted in an end of the connector assembly to pass into the slots 54 and openings 53. The strip 48 is advanced or moved to the final position where it may extend throughout the entire length of the connector. The strip 48 engaged in the slots 5 and openings 53 positively locks the member 41 against transverse displacement and lateral separation. The interfltting serration 52 secure the sections C against relative longitudinal movement The present invention provides structural conmotors that are 'easilvand quickly assembled Without the necessity of using multiplicities of screws, rivets or the like, and without the use of special tools; The connectors are positive when assembled and are capable of withstanding heavy loads in all directions. The connectors are such that the joints may be flush and without irregularities of any kind whatsoever.

Having described only typical forms of the invention I do not wish to be limited to the speciflc details herein set forth, but wish to reserve said plane and presenting opposing forward faces, serrations on the opposite forward faces of the flange parts extending in a direction generally transverse of said edges and adapted to mate to hold the elements against relative longitudinal movement, longitudinally extending bulbs on the rear faces of the flange parts, and a channel key slid onto the flange parts to hold their serrations in mesh and having bulbs for cooperating with the first named bulbs to prevent relative transverse'movement between the elements, the channel key presenting a surface occupying said plane to be flush with said faces and substantially closing the space between said faces.

2. A connector for securing two elements together in assembled relation comprising a member to be attached to each element to extend along an edge thereof, a channeled flange part extending flange, serrations on opposing faces of said outwardly extending flanges in a generally transverse direction and adapted to mate to hold the elements against relative longitudinal movement, and a channel shaped key engaged between said inwardly and outwardly extending flanges of the flange parts to hold the serrations in mesh and to prevent relative transverse movement of the elements.

3. A connector for securing two elements together in assembled relation comprising a member 'to be attached to each element to extend along an edge thereof, a channeled flange part extending longitudinally of each member at the inner side of its respective element, serrations on opposing faces of the flange parts extending in a generally transverse direction and adapted'to mate to hold the elements against relative longitudinal movement, and a channel key engaged in said channeled flange parts to hold the serrations'in mesh and to prevent relative transverse movement of the elements, said key presenting a surface that is substantially flush with the outer faces ofthe elements. a

4. A connector for securing two elements together in assembled relation to have corresponding faces in a common plane comprising a member to be attached to each element to extend along an edge thereof, a channeled flange part extending longitudinally of each memebr at the inner side of its respective element, serrations on opposing faces of theflange parts extending along an edge thereof, a channeled flange part extending longitudinally of each member at the inner side of its respective element, the flange parts having channels facing outwardly toward said plane, serrations on opposing faces of the flange parts extending in a generally transverse direction and adapted to mate to hold the elements against relative longitudinal movement, bulbs in the channels of said parts, a channel key removably engaged in said channels to hold the serrations in mesh, and bulbs on the key cooperating with the first named bulbs to prevent relative transverse movement of the parts.

6. A connector for securing two elements together in assembled relation to have corresponding faces in a common plane comprising a member to be attached to each element to extend along an edge thereof, a channeled flange part extending longitudinally of each member at the inner side of its respective element, the flange parts having channels facing outwardly toward said plane, serrations on opposing faces of the flange parts extending in a generally transverse direction and adapted to mate to hold the elements against relative longitudinal movement, bulbs in the channels of said parts, a channel key removably engaged in said channels to hold the serrations in mesh and presenting a surface that is flush with said faces of the elements, and bulbs on the key cooperating with the first named bulbs to prevent relative transverse movement of the parts, the first and second named bulbs being notched so that the key may be entered into said channels in a transverse direction and then moved longitudinally to engage the second named bulbs under said first named bulbs.

ANDRE CROT. 

